New Deposition Method Developed

Researchers at Penn State have developed a method to apply a gas-tight layer of zirconia on solid oxide fuel cell tubes. "There must be a gas-tight layer between the hydrogen-rich fuel and the oxygen, otherwise, when they meet, there will be an explosion," explains Rajendra N. Basu, postdoctoral associate in materials science and engineering. "Putting down a gas-tight layer can be accomplished using electrochemical vapor desposition, but it is a very expensive, time consuming and complicated process."

The researchers are using electrophoretic deposition with a difference that seems to work. In electrophoretic deposition, a suspension of yttrium-doped zirconium oxide powder is made on very high concentration acetic acid. The application of an electrical potential allows the charged powder to move towards and deposit on the electrode with the opposite charge. The object, with the powder coating, is then fired at a very high temperature so that the coating forms into a continuous film on the underlying material.

However, depositing zirconium oxide on the bare porous ceramic cathode tube surfaces of the tubular solid oxide fuel cells leads to an inhomogeneous coating that is not gas tight. The researchers deduced that the pores of the cathode tube were the source of the problem and decided to try a fugitive layer of carbon between the tube and the coating. This graphite layer serves as a uniform cathode and the zirconium oxide deposits evenly on the surface. During firing, the graphite sublimes and the coating deposits evenly on the tube's surface.

For more information, contact Andrea Elyse Messer at (814) 865-9481 or e-mail aem1@psu.edu.

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